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A Fallen Comet

From written language to the Pyramids, ancient Egyptians’ contributions to the modern world are too numerous to list. But a recent study in Earth and Planetary Science Lettershas added a new item to their legacy. A brooch belonging to King Tutankhamun has led scientists to a rather unexpected find – the first fallen comet ever discovered on Earth.

The centerpiece of this brooch is a large piece of yellow glass carved into the form of a scarab beetle. This ‘jewel’, composed of silica glass, is one of thousands of such artifacts scattered over 6000 square kilometers (2300 square miles) of the Sahara desert. It has long been suspected that this debris field formed from the collision of a celestial body with Earth approximately 28 million years ago, however no trace of an impact crater has ever been found.

The yellow glass objects, known as ‘tektites’, are commonly produced by the high pressures and temperatures produced by meteorite impacts. However, isotopic analysis of a black stone found among the debris shows that it bears the same carbon and argon ‘signature’ as a comet. While hundreds of meteorites are found every year (what we call shooting stars are in fact meteors burning up in the Earth’s atmosphere), the chances of a comet hitting Earth are slim, and the chances of finding its record – even slimmer. In 1994, the comet Shoemaker-Levy 9 collided with Jupiter – the only event of its kind ever recorded.

So what makes comets and meteors so different? Meteors are essentially rock fragments in space, formed during collisions of planets or asteroids. Comets, on the other hand, are composed mainly of ice and dust. While more than 50,000 meteors have been found on Earth to date, less than 5,000 comets have been identified in our Solar System. And while it is likely that comets have hit Earth over its 4.5 billion year lifetime, their composition makes it unlikely for these impacts to be preserved. While small meteors may burn up completely in the atmosphere, larger ones reach the Earth’s surface intact and, with enough experience, are easy enough to identify. However, the ice core of a comet would vaporize in the atmosphere, and only dust would reach the Earth’s surface, leaving barely a trace of the impact behind.

This is exactly why King Tut’s ‘treasure’ is so exciting. Once verified, this find could give us a glimpse into space and cosmic history that we yet know little of.

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